As molded catalysts, honeycomb type catalysts have been known in the past, and they are known as catalysts for removing nitrogen oxide from coal or heavy oil exhaust gas (NOx removal catalysts), catalysts for removing nitrogen oxide from automobile exhaust gas, catalysts for removing particulate substances from automobile exhaust gas (Japanese Patent Laid-Open Publication No. 147218/2002, patent document 1), sulfide oxidation catalysts, fuel treating catalysts for fuel cells (e.g., methanation catalysts), deodorization catalysts (Japanese Patent Laid-Open Publication No. 299558/1989, patent document 2), etc.
The honeycomb type catalysts mainly include a honeycomb type catalyst obtained by kneading an oxide powder containing a catalyst component and extrusion molding the kneadate and a honeycomb type catalyst obtained by forming a carrier layer on a metal or ceramic honeycomb substrate and allowing the layer to support a catalyst component or forming a catalyst layer on the honeycomb substrate surface.
In the case of the former catalyst, strain or deflection is liable to occur, or when it is dried or calcined, cracking is liable to occur, and therefore, it is difficult to obtain a large honeycomb catalyst. In the case of the latter catalyst, it is difficult to form a carrier layer and/or a catalyst layer having excellent adhesion on the metal or ceramic honeycomb substrate surface.
On this account, in the former case where an oxide powder is used, use of a fibrous substance such as glass fiber or organic fiber has been carried out (Japanese Patent Laid-Open Publication No. 213442/1984 (patent document 3), Japanese Patent Laid-open Publication No. 36080/1987 (patent document 4)). In this method, strain, deflection, cracks, etc. can be reduced to a certain extent, but it is difficult to remove them completely, and in order to enhance productivity, further improvement has been desired.
In the latter case where a carrier layer is formed, it has been proposed to form protrusions on the honeycomb substrate surface (Japanese Patent Laid-Open Publication No. 169111/2004 (patent document 5)). Also in this method, however, adhesion of the carrier layer or the catalyst layer is insufficient, and when the catalyst is used over a long period of time, there occurs problems of lowering of catalytic performance and occurrence of separation of the carrier layer or the catalyst layer.
As a method for generally forming a fine particle layer on a substrate of a simple structure such as a flat plate substrate, a photoelectric conversion element for photovoltaic cell obtained by depositing semiconductor fine particles in a layer form on a conductive substrate by electrophoresis has been disclosed (Japanese Patent Laid-Open Publication No. 100416/2002 (patent document 6)).
Further, a method for producing an electrodeposited grindstone having a high-density abrasive grain layer by elelctrodepositing metal oxide-coated diamond abrasive grains on a substrate has been disclosed (Japanese Patent Laid-Open Publication No. 254866/2000 (patent document 7)).
Moreover, a fluororesin-containing porous body for gas diffusion electrode, which is obtained by depositing fluororesin fine particles as gas diffusion electrode materials on a surface of a conductive substrate by electrophoresis, has been disclosed (Japanese Patent Laid-Open Publication No. 121697/2002 (patent document 8)).
Patent document 1: Japanese Patent Laid-Open Publication No. 147218/2002
Patent document 2: Japanese Patent Laid-Open Publication No. 299558/1989
Patent document 3: Japanese Patent Laid-Open Publication No. 213442/1984
Patent document 4: Japanese Patent Laid-Open Publication No. 36080/1987
Patent document 5: Japanese Patent Laid-Open Publication No. 169111/2004
Patent document 6: Japanese Patent Laid-Open Publication No. 100416/2002
Patent document 7: Japanese Patent Laid-Open Publication No. 254866/2002
Patent document 8: Japanese Patent Laid-Open Publication No. 121697/2002